TOSLINK optical cable connections

We already covered TOSLINK in the blog post SPDIF connections: Get connected, not confused. Of the connections mentioned that are capable of transporting a digital signal — HDMI, coax and TOSLINK — TOSLINK is perhaps the least understood and strangest. A cable connection that transmits signals as light impulses? We’ll explain.

Optical cables: A reliable way to transmit digital signals

TOSLINK is a well-established method for transmitting digital audio data. You’ll find TOSLINK connections on receivers, amplifiers, televisions, game consoles, CD players and computers. A TOSLINK cable uses optical signals and is therefore also known as an “optical cable.”

The name TOSLINK stems from the company name “Toshiba” and the word “link.” The Japanese electronics concern developed this optical transmission medium back in the 1980s as a way to send digital signals from its CD players to speakers. Since that time, TOSLINK has grown into a cross-platform connection standard.

Here’s how it works: Light conveys the digital signal through special fiber optic cables as either the presence or absence of light. In this system, a light impulse represents a one and the absence of light a zero. The source device converts the digital signal into the appropriately coded pulses of light and sends it along the light-conducting fiber cable to a receiver on the playback device such as a TV where is converted back into to a digital signal. Light naturally suggests itself as a medium for digital signals because of the speed with which it travels and the ability to represent zeros and ones by the simple presence or absence of the light impulse.

TOSLINK optical connections
The back connection panel on the Teufel Cinebase with optical TOSLINK input.

How to use TOSLINK cables

TOSLINK cables are an easy and reliable way to transmit digital audio signals. Simply connect the square cable ends (in audio circles, sometimes referred to as the F05 specification) to the appropriate input. The great advantage of optical connections is their resistance to signal disruptions. With electricity-based connections, for instance, unwanted noise is sometimes added to the audio signal in the form of ground loops. Since TOSLINK uses light instead of electricity to transmit a signal, it’s not susceptible to ground loops as are, say, RCA connections.

Speaking of RCA connections, there is a variety of mini TOSLINK that looks like a 3.5 stereo jack. Unlike RCA inputs, however, the mini TOSLINK input on your laptop or iPod will need to be specially equipped to process the optical signal. However, on some devices the RCA and TOSLINK inputs are combined. Adapters are also available that make it possible to connect regular-sized TOSLINK cables to mini TOSLINK inputs.

Is TOSLINK being replaced by HDMI connections?

TOSLINK, like a digital coaxial connection, is compatible with the SPDIF interface. Based on its ability to handle relatively large data volumes and transmit multiple channels, SPDIF was the go-to connection for hi-fi and home cinema sound for years. However, the enormous data volumes that new HD sound standards require place restrictions on SPDIF connections. The surround sound formats Dolby Tue HD and DTS HD, for instance, can be transmitted via TOSLINK and coaxial connections but in a downmixed form. In order for the full data volume to be transmitted, an HDMI connection is required.

Not only does HDMI transmit full and uncompromised HD audio files, it’s capable of carrying the video data as well – all in a single cable. Manufacturers have responded to HDMI’s superior transmission capabilities by increasing the number of HDMI inputs they offer and, in some cases, doing away with TOSLINK connections completely. Apple’s digital media player, Apple TV, for instance no longer offers a TOSLNK connection. Those wanting to connect the device to an AV receiver or amplifier will need to make sure these devices have HDMI inputs.  Thankfully, all new models generally do and older models can be connected via HDMI audio splitters. It remains to be seen whether other manufacturers will go the way of Apple and eliminate the TOSLINK option. Newer Teufel devices like the CoreStation compact AV receiver continue to offer a wide range of options including a coaxial input, 2 optical inputs, 1 RCA input, 2 RCA mini jack inputs and 4 HDMI inputs and 1 HMDI video output for maximum flexibility.

TOSLINK cables: An overview

  • TOSLINK is a method for transmitting digital audio signals via light impulses
  • The method is well established due to its high degree of stability and low susceptibility for noise interference
  • Optical cables come in two varieties: A standard square plug and a miniplugs that resembles RCA jacks
  • The bandwidth offered by TOSLINK is not large enough to transmit HD surround sound formats
  • HDMI splitters can help with source devices that do not offer TOSLINK connections

Title Picture: By Ruben58 (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

TOSLINK optical cable connections
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